Every interview I've attended has resulted in a job. It's very naive and maybe even arrogant to believe that if you don't wear a suit to an interview you wont get a job. As long as you don't take the micky and wear jeans and a T-shirt, there are far more important things prospective employers look for, other than what the candidate is dressed like!
Similar situation with me. I recently went for a scientific analyst post and wore a shirt, tie and trousers but no suit and got the job despite immense competition. When I asked my employer what sort of clobber I should wear in the role, he told me shirt and jeans are fine and "...had you turned up for interview in a suit, I'd have held it against you".
Not all employers insist on adhering to old-fashioned dress code - thankfully!
Granted, but in today's job market you need to do everything you can do stand out from the other candidates.
That's true, but 'standing out' and 'setting a positive impression' are not one and the same.
If you're applying for an office-based role within, say, a bank or in management, maybe a suit suggests the right attention to detail (in an arena where the suit label and colour of the buttons matters) but in most jobs I've worked in, they want people to look like they've made an effort (ie: are clean, tidy, can use an iron) but primarily have the skills and the knowledge for the position.